Extended-Spectrum β-Lactamase (ESBL)

CTX-M dendogram fragment
Typing Services

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$40 for PCR set , $50 for each ST

As highlighted in a recent CDC report (1), the emergence and spread of antibiotic resistant bacteria represent major threats to the health of the American public. Major culprits are the enterobacteria (family Enterobacteriaceae, particularly KlebsiellaE. coliSalmonellaShigellaProteusEnterobacter, and Serratia species) and their distant relatives Pseudomonas and Acinetobacter species. Not surprisingly in light of their widespread use, beta-lactam antibiotics (penicillins, cephalosporins, monobactams, carbapenems) represent the major target of resistance mechanisms. In the Gram negative species noted above, the resistance mechanism typically involves plasmid-mediated acquisition of one or more beta-lactamase (bla) genes.


Since the 1980’s, many novel bla genes have emerged that confer resistance to extended spectrum beta-lactams including aztreonam and third generation cephalosporins (e.g., cefotaxime). This epidemic spread of extended spectrum beta-lactamases (ESBL) has been labelled a “serious” threat by the CDC. In the U.S., the most commonly encountered ESBL fall into five groups: CTX-M-1, CTX-M-9, SHV, TEM, and CMY (the latter group also classified as AmpC cephalosporinases). Less common are the the FOX, OXA-1, CTX-M-2, CTX-M-8, and CTX-M-25 groups.


One of the four core actions in the CDC plan to address these multiple threats is “tracking resistant bacteria”. Of course, this tracking remains heavily dependent on conventional antimicrobial susceptibility testing of cultured organisms. While these susceptibility data are important, accurate tracking requires identification of resistance mechanisms at the genotype level, since the resistance phenotype can be mediated in multiple ways. Genotyping begins with a PCR screen to identify the resistance gene(s), followed by sequence typing to identify the specific allele (see, for example, ref. 2).


MicrobiType offers a comprehensive panel of PCR screens and sequence typing services to assist in the genotyping of beta-lactam resistance mechanisms in Enterobacteriaceae, Pseudomonas, and Acinetobacter species. These services employ genomics-optimized modifications of previously published primer sets to maximize both reliability and affordability. ESBL-related services are listed here; see also the Carbapenemase page.


ESBL-1-PCR screen for the 5 most commonly encountered groups of ESBL genes: CTX-M-1, CTX-M-9, CMY, SHV, and TEM. Results are reported as positive or negative for a given ESBL group.

ESBL-2-PCR screen for 5 less commonly encountered groups of ESBL genes: CTX-M-2, CTX-M-8, CTX-M-25, FOX, and OXA-1. Results are reported as positive or negative for a given ESBL group.

ESBL-ST (list above):  Samples that are PCR positive for a given ESBL are further characerized by genomics-optimized sequence typing. Results are reported as sequence type (i.e., allele number) based on comparison to ESBL databases (NCBI and lahey.org/studies). Additionally, a dendrogram is provided to illustrate the relationship of the sample allele to concurrently or previously submitted alleles from your lab, and to a representative panel of previously characterized alleles; see ESBL-1 dendrograms and ESBL-2 dendrograms for examples.

Note that for each service substantial discounts are applied for multiple isolates.

(1) www.cdc.gov/drugresistance/threat-report-2013
(2) Castanheira M et al. (2013). Antimicrob Agents Chemother 57:3012.

(MicrobiType services are for research/investigational use only.)